This section discusses some of the buttons on Nav Camera's main screen.

Tap the "PREFS" button to see settings for the compass (true or magnetic), units (ft or m), datums, and position format. This section of the app also provides a link to this help page.

This button toggles colored lens filters over the screen, which may be helpful to preserve night vision or improve usability in low light situations. Available colors are red, green, gold, and gray. The same button toggles the display back to normal.

This button toggles the zoom level of Nav Camera's main display -- and any captured photos or movies -- between 1X, 2X, and 4X.

This button is used to change the app's camera mode and options.

Tapping this button lets you control features of the photo/movie overlay, such as content and color. You can also edit custom notes that will be rendered into the overlay.

Tapping this button will show realtime hardware and sensor status, and give accuracy numbers for the various sensors and data measurements.

Tap the center reticle to cycle between the available options. Current reticles include three types of crosshairs and an SLR-style focus/exposure indicator.

When pressing the shutter button (denoted by a photo camera icon when in photo mode) Nav Camera captures a still image at the camera's maximum resolution, and will optionally overlay the image with a center crosshairs and a data stamp showing date, time, geo-data, datum, zoom level, and custom notes. The overlay font is scaled to the image size, and has settings for white, yellow, or green colors (all rendered with a transparent black drop shadow for legibility on any background). If available on the device, the flash can be used in manual or automatic mode.

Image saves are buffered and done in a background thread, so that you can continue to shoot photos while image saves are in progress. With multitasking, image saves will continue after you leave the app. Images are saved to the device photo album, and are written with an EXIF metadata record containing position, altitude, bearing, GPS datum, and user notes.

When pressing the record button (denoted by a movie camera icon when in movie mode), Nav Camera records a movie. Movie mode is similar to the photo mode, recording a basic video with options to show an overlay with crosshairs, geo-data, datum, zoom level and custom notes. Movie mode offers multiple video quality settings, and will record audio along with video. On capable devices, the torch can be used for lighting the video scene in movie mode.

On devices capable of HD recording, there are three video quality settings. Low records 4:3 at 480x360, medium records 4:3 at 640x480, and HD records 16:9 at 720p or 1080p (whichever the device supports).

On devices that do not support HD recording (such as the iPhone 3GS), only two video quality settings are available. Low records 4:3 at 480x360 and high records 4:3 at 640x480.

Movie capture occurs in two stages; first, the movie is recorded, and then it is processed to add information such as overlays. For the best performance, processing is run in the foreground as a modal task. If recording or processing are interrupted (such as by a phone call or other multitasking event in iOS) Nav Camera will give you the option to process an interrupted recording, resume processing the movie, or delete the movie once you return to the app.

After a movie has been processed, it is saved in a background thread and you can continue using Nav Camera, or leave the app, while the save is in progress. Movies are saved to the device photo album as ".mov" files, using H.264 video encoding and AAC audio recording (with audio bit rates ranging from 700 kbps to 10.5 mbps).

Warning: Recording and processing movies in Nav Camera is extremely computationally intensive, so this feature must be used carefully and wisely. It is not intended for extended movie recording or continuous monitoring, but rather, for short recordings (in the range of 10-20 seconds) in scenarios where Nav Camera is typically used to make measurements or document observations and findings.

For the fastest performance, use the regular movie mode with lower video quality settings. In this mode, processing will take 1-4 seconds for every 1 second of recorded video on a typical device. This processing overhead can stretch to as much as 5-10 seconds of processing per 1 second of recording when using HD mode on an older device.

It's advisable to experiment with your device in typical usage scenarios, to find the right balance between quality and processing time. Medium video quality is sufficient for most purposes. HD quality is mainly intended for recording movies in cases where wide screen format or crisp overlay graphics are desired, and/or in cases where the user is willing to accept the additional processing overhead to get maximum video quality.

To see the current reported accuracy of hardware and sensors, tap the STATUS button on the screen. The accuracy of position, altitude, and azimuth measurements in Nav Camera are determined by the hardware capabilities of your device, the location of measurement, and the quality of GPS signals and sensor readings.

Under optimal conditions (clear line of sight to the sky with signals from at least four satellites), the newest iOS devices generally have a position accuracy of 10-15 feet and an altitude accuracy of 15-20 feet.

With no magnetic interference, the latest iOS devices can generally measure azimuth with an accuracy of 5-10 degrees.

All accuracy numbers reported in Nav Camera are based on hardware specs and realtime accuracy information provided by Apple through iOS. The application itself does not determine or influence accuracy; however, the displays in Nav Camera are setup to show levels of fidelity, resolution, and proper number of significant digits that are appropriate for the available hardware accuracy.

The optional Datum Pack adds over 220 geodetic datums to the app, covering regions around the world. These datums are used to compute position and altitude from GPS data. The Datum Pack is available with an additional one-time in-app purchase of $2.99 USD (or equivalent) through the iTunes App Store.

The default datum used by iOS location services, and Nav Camera, is WGS-84 (WGS stands for "world geodetic system" and 84 refers to "1984", the year of this standard). WGS-84 is an ellipsoidal model that approximates the surface of the Earth.

While WGS-84 is a good worldwide compromise for a datum, any datum that attempts to model the entire Earth with a single ellipsoid will have errors in regions where the Earth's actual surface deviates from the ellipsoidal shape. For that reason, local datums are often used in navigation and surveying. These allow a more accurate representation of the Earth surface over smaller regions of interest. Well known datums in North America are NAD-27 and NAD-83, which have subsets covering specific regions like Alaska, Canada, Mexico, and other regions and countries in North America. In Europe, OSGB-36 is well known in the United Kingdom, and ED-50 is commonly used in other European countries.

Nav Camera's optional Datum Pack includes over 220 additional datums, covering regions and countries on all continents around the world. You can browse this list by opening the preferences screen via the PREFS button and tapping on the "Geodetic Datum..." button. You can purchase the Datum Pack, which includes all datums shown in the list (as well as any future additions), by selecting any non-default datum in the list. You will be prompted to complete a one-time in-app purchase through the iTunes App Store to install the Datum Pack feature. This purchase is transferable to all of your devices running Nav Camera under your iTunes account (note, however, that the in-app purchase is not transferable between other apps by Hunter Research and Technology, as they are separate products in iTunes).

Once installed, you can select any datum that is part of the Datum Pack, and Nav Camera will use the datum to convert raw GPS data into position and altitude. Most regional datums have a limited range of applicability; if you are in a position outside of that range, the status indicator on Nav Camera's main screen will turn red and the status screen will show "Datum location outside of limits." This doesn't necessarily mean that computed position and altitude are wrong, but it does suggest that the active datum is not going to provide accurate results, so another datum is likely more appropriate.

Nav Camera's Datum Pack has an architecture that will easily accept additional datums in future releases (at no extra charge). If you would like to use a datum that is not currently included, or have any other feedback on datums, please let us know.

Note: if you have a question/issue not addressed by the FAQ, please contact the developer.

First, try rebooting your device. If that doesn't solve the problem, delete the app and reinstall it. This is an iTunes issue, and not specific to Nav Camera.

When you attempt to access the photo album from an app for the first time, you will see a popup alert from iOS asking you to give permission to the app. Many people are clicking the wrong button, which actually denies Nav Camera permission to use the photo album and prevents it from saving photos or movies. To override this, go to System Settings > Privacy > Photo and give the app permission there. The photo permission requirement and popup are part of iOS, not Nav Camera, so please direct feedback about this to Apple.

When you attempt to launch an audio-visual app in iOS 7 for the first time, you will see a popup alert from iOS asking you to give permission to use the microphone. Many people are clicking the wrong button, which actually denies Nav Camera permission to use the microphone and causes movie recording to be disabled. To override this, go to System Settings > Privacy > Microphone and give the app permission there. The microphone permission requirement and popup are part of iOS, not Nav Camera, so please direct feedback about this to Apple.

This is a symptom of low memory. Nav Camera needs as little as 10MB to launch and about 70MB to process photos, which is small compared to the 512-1024MB memory built into newer iOS devices. So the low memory condition is likely caused by other apps running on your device in the background. To solve the problem, you can either force quit other apps, or simply reboot your device. If the problem happens again, you may want to determine which background app is the culprit -- it could be leaking memory or simply be using too many resources.

Yes, in fact any location-aware app will work with these accessories -- no special modifications are needed. Many Nav Camera customers use the BadElf, Dual, and Garmin GPS modules with iPads and iPod Touches that do not include built-in GPS hardware.

Please check System Settings under Privacy > Location Services and make sure you are allowing Nav Camera to use location data. Many people turn this off without realizing it. Be aware that you need a clear line of sight to the sky to receive GPS location data, and a network connection is required for fast GPS refinement. Without a network connection, GPS location data is still available, but the initial location fix will take much longer (tens of seconds or even minutes). This behavior is characteristic of the device's location services implementation and not controlled by Nav Camera itself.

Only the iPad 3G/4G models and iPhone can display altitude. Wifi-only iPads and iPod touch devices cannot. For these devices to receive proper altitude data from GPS, they must have a clear line of sight to four satellites in the sky. Altitude may not be available if you are indoors or if your view of the sky is obscured. In marginal cases, you may receive position data but no altitude.

Only iPads and iPhones can display azimuth/bearing, since they have magnetometer (compass) hardware. iPod Touch devices do not contain a magnetometer. If your compass-equipped device is not showing compass data, or the data is not updating, your device is probably being affected by electromagnetic interference. The magnetometer is susceptible to interference inside cars, near metal objects/structures, or near electronic equipment. Try moving to a different location, and wave the device in a figure eight motion to recalibrate the magnetometer.

Unfortunately, gyro-derived azimuth is not robust enough to be accurate by itself, due to gyro drift. After setting a North reference, motion and rotation of the device would cause it to drift from the reference over time, and eventually become totally inaccurate. This can occur in as little as one 360 degree rotation, resulting in errors of 30-60 degrees or more. Therefore, Nav Camera eschews this approach in favor of combined gyro-compass fusion. The fusion algorithm in Nav Camera gives the best of both worlds, providing fast response and accurate measurement from the gyro during dynamic use of the device, with periodic corrections from the magnetometer to eliminate drift.

Tap the STATUS button to see the hardware status. Accuracy of data received from the device's hardware will be shown. The app's accuracy is limited by what the hardware can provide. For good GPS data, make sure you have a clear line of sight to the sky. For good compass data, be sure you are away from any sources of electromagnetic interference. Note that the iPhone corrects altitude data based on an ellipsoidal model of the Earth's surface, so altitude is only approximate in most cases. This is an inherent limitation of GPS. Position and altitude computation can be improved significantly with the optional Datum Pack in-app purchase.

Position coordinates can be displayed in several ways in the app. Some of the lat/lon position formats in Nav Camera use an "absolute" reference system, with North latitude and East longitude taken as positive directions. Other lat/lon options use a relative coordinate system, expressing positive latitudes as North, negative latitudes as South, positive longitudes as East, and negative longitudes as West.

The GPS and location hardware in all iOS devices (and most consumer GPS devices) defaults to the WGS-84 ellipsoid. Nav Camera offers an optional Datum Pack that includes over 220 additional datums that can be used in the app.

First of all, make sure the real compass is not near your device, as it can interfere with the compass needle and throw it off. Then make sure you have switched Nav Camera to display magnetic north so that it will be consistent with a real compass. For accuracy of the device's compass, tap the STATUS button. The iPhone compass accuracy is generally in the range of 5 to 10 degrees, but can be as poor as 20 or 30 degrees if there is electromagnetic interference.

Go into your device's settings, under Privacy > Location Services. Scroll to the bottom, and select "System Services". Make sure that the "Compass Calibration" option is turned on. This is required in order for Nav Camera to get magnetic declination information from GPS, which is used to compute a TRUE direction. If you have this turned off, or if you are not allowing access to location services, only MAGNETIC direction can be used in Nav Camera.

Yes. Nav Camera saves position, altitude, bearing, datum, and user notes in the EXIF metadata.

Due to limitations in the iOS SDK, this feature is not currently available, but we hope to add it in a future version of Nav Camera.

When taking photos from the app, it takes anywhere from 1-4 seconds to process and save the image to your photo album depending on your device and how large of a photo it takes. This work is buffered and done in a background thread, so that you can continue to shoot photos while image saves are in progress. With multitasking, image saves can continue after you leave the app.

Apple has never approved this feature for third-party apps. While some apps manage to sneak the feature past Apple review, others are rejected and not allowed to go on sale in iTunes. We do not plan to implement this feature and risk rejection from iTunes, but will gladly implement it if Apple approves the feature for third-party apps at some point in the future.

If you need assistance or have feedback, please contact the Nav Camera developer at:

dev@hunter.pairsite.com
Feature requests, comments, and suggestions are welcome. Many of the features in Nav Camera started as customer requests, so your input is valuable.

If you like Nav Camera and find it useful, please leave a review on iTunes. Long term development of this app depends on having a strong, involved customer base. iTunes reviews help establish the app and improve sales, which in turn provides financial support for continued development. Please consider leaving a review. Customers who have written reviews for previous versions of Nav Camera can update/revise their reviews after downloading new versions of the app. Thanks for your support!

Developed by Dr. Craig A. Hunter
Copyright © 2014-2018
Hunter Research and Technology LLC